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Abstract

Sand scorpions make burrows from which they emerge at night to seek mates and prey. Previous ecological studies have documented scorpion activities on the sand surface. Few studies, however, have videotaped scorpion movements in the context of understanding their sensory neurobiology. Our objective is to understand which signals guide scorpions as they emerge from and return to their burrows. Candidate stimuli include chemical trails, footsteps, celestial patterns, geomagnetic cues, humidity and/or temperature gradients, distinctive scents from the burrow, seismic echolocation, memory, or landmark orientation. We videotaped scorpions to learn whether they return to their burrows by the same path they use as they exit, or whether they use a different route. The answer to this question could help eliminate some of the candidate stimuli from consideration. We used pole-mounted infrared surveillance cameras that relayed images to a digital recorder to monitor and record the movements of sand scorpions (Paruroctonus utahensis) near Monahans, Texas. Two-hour recording blocks of two animals on two consecutive nights revealed that the animals spent most of their time at the thresholds of their burrows, usually emerging briefly after an arthropod walked by. In each case, the scorpions took a looping path that did not retrace the route by which they exited their burrows. In additional experiments we used small lures to seismically entice scorpions from their burrows and monitored their movements as they returned to their burrows. These studies and other observations suggest that many of these sand scorpions do not spend much time on the sand surface; instead, they wait at the threshold of their burrows and ambush prey that wanders nearby.